Quality is delighting customers
Consider this Ex: You need to test a program that checks whether input filename is Correct or not. As per the specification, the the file name can have 1-7 letters (A-Z), only in the upper case. Digits, Spl Chars and Space in between are not allowed.
So the possible input which u can give to test this are file names with 1 letter, 2,3,4,5,6,7 letters. Each letter can be one of the 26 alphabets in the Upper Case and all these are Valid inputs. So the no of valid inputs u need to give are:
In addition to these u need to give some inputs like 8 digit filename, few with spaces, some spl chars, sumbols and digits. For all these it should throw an error message.
So you conclude that this type of Exhaustive Testing is practically Impossible.
So As an alternate, u will have only few valid inputs filenames and few invalid set of file names and test the software and get confident that its working fine.
Hope i made u understand what is Exhaustive Testing.
Ya Umesh I got it... Thanks you very much :)